Process and apparatus for exothermic catalytic reactions



' beneath the casing Patented Sept. v7, 1926.-

'HARRY n. GIBBs, or' rENNs GaovE, NEW NEMOURS a COMPANY, or WILMINGTO WARE.

PROCESS AND APPARATUS FOR EXOTHERMIC CATALYTIC REACTIONS.

Application led July 27,

This invention relates to catalytic oxidation apparatus and process, and comprises an apparatus which, although of relatively large capacity, is so constructed as to b e operable under precisely controlled conditions.

It is well-known that many oxidation reactions are exothermic, and it is very dilicult to carry on these reactions on a large scale practicable for commercial operatlons, and remove the large amount of heat generated in the process of the reaction. It is also well-known that many ofl these reactions will proceed in very satisfactory manner on a smaller scale, but on a large scale, the concentration of the large amount of heat in the apparatus results in the destruction of the apparatus or the raid combustionl of the desired products o 4the reaction, resultin in unsatisfactory yields.

One 0f the o jects of my invention is to provide a large scale apparatus wherein the ease of controlling the reaction which is characteristic of small scale operations may be retained.

Other objects of the invention will become apparent from the following description.

One embodiment of my invention is shown in the accompanying drawings in which Fig. l is a diagrammatic view of a horizontal section through the ap aratus, and Fig. 2 shows a rear elevation with 'part of the condenser broken away.

The apparatus comprises a casing 2 having in the front end a header or manifold 3 provided with the curved surface 4, and

at the other end a conduit 6 leading into a condenser 7. Extending lengthwise through said casing, and equally spaced apart, are tubes 5 adapted to be partly illed with catalytic material. Surrounding the pipes 5 and filling the interior of the casing 2 is a medium 5a of high heat conductivity. The condenser 7 is provided with an outlet 8 leadingv to any suitable recovery apparatus. A burner 9 is disposed 2, both the burner and the casing being supported by brick-work or other sultable frame-work 10. An inlet pipe l for introducing a fluid into the apparatus extends into the conduit 6 and through the center of the casing 2. Y

1920. Serial No. 399,354.

The operation may be described with reference to the catalytlc oxidation of naphthalene to phthalic anhydride. The interior of the casing 2 having been filled with a material ofvhgh heat conductivity', such as a mixt-ure of sodium and potassium nitrates, and the tubes 5fbeing partly lled withl an oxidation catalyst such as vanadium oxide, the casing 2 and its contents are heated by the burner 9 until the temperature reaches about 500 C. A. mixture of air and naphthalene vapo-rs is then conducted by the pipe `1 through the casing 2, where it becomes preheated, and into the manifold 3 andthen through the catalytic tubes 5, where the naphthalene is oxidized to phthalic anhydride. The mixture of nitrogen, unused oxygen and phthalic anhydride vapor passes into the condenser 7 where the phthalic anhydride condenses and is separated from the permanent ases, the latter escaping through the ue 8.

vAs soon as the oxidation is well started the burner 9 c an be shut od, the heat of the reaction being more than suiiicient to maintain the temperature at 500 C. Instead of a mixture of sodium and potassium nitrates as the heat conducting medium in the casing 2, there may be used various other heat conducting materials, either solid or liquid, for example, `other fused salts, materials of high boiling points, such as molten metals, etc.

The curved surface 4 of the manifold 3 should be such as to distribute the gases uniformly to the several catalytic tubes 5; the best distribution of gases is obtained when this surface is a parabola -of revolution.

With the apparatus above described the catalytic/oxidation of a large amount of a hydrocarbon vapor. such as naphthalene vapor can be effected in a short time, ordinarily at temperatures above 200 O. without losses due to local overheating of the catalytic material with corresponding de- .J'ERSEY, ASSIGNOR TO E. I. DU PONT DE- N, DELAWARE, A CORPORATION 0F DELA--Y composition of the substances to be oxidized.

This desirable result is due to the fact that the medium 5", of high heat conductivity, permits of a rapid and uniform conduction throughout the apparatus of the heat generated in the excess heat being radiated or dissipated about as fast as it is generated. The cata'- several catalytic tubes, the

lytic material is in this way maintained at a uniform temperature throughout the casin 2. v

llthough I have described and shown in detail one specific embodiment of my invention, it will be understood that the apparatus may be changed in various respects without departing from my invention. Thus, the condenser 7 maybe shaped in various Ways, depending largely upon the material roduced as a result of the catalytic oxi ation. Although the re-heating of the vapors by passing them t rough the casing 2 is desirable, it is not an essential feature of my invention.

-.1. The process of producing phthalic anhydride by the catalytic oxidation of naphth'alene which comprises passing a mixture of naphthalene vapor andan oxygencontaining gas through a plurality of relatively smal, catalytic reaction zones containing an oxidation catalyst at a temperature of from about 400 to 600 C., and causing rapid dissipation of heat in excessof that required to continue the reaction by maintaining said zones in contact with a medium of high heat conductivity. 2. The rocess of producing phthalic anhydride liy the catalytic oxidation of naphthalene which comprises passing a mixture of naphthalene vapor and an oxygencontaining gas through a plurality of small, hot catalytic reaction zones disposed in -a medium of high heat-conductivity.

3. The process of producing phthalic anhydride by the catalytic oxidation of naphthalene which comprises passing a mixvture of naphthalene vaporand an oxygencontaining gas through a plurality of small, hot, catalytlc reaction zones evenly disposed in a medium of such high heat .conductivity as to dissipate excess heatl and to maintain said zones at a uniform reacting temperature. y. j

4. The process of producing phthalic anhydride by the catalytic oxidation of naphthalene which comprises passing a. mixture of naphthalene vapor and air through a plurality of relatively small, catalytic reaction zones at a temperature between about 400' and 600 C., and causing rapid dissipation of heat in excess of that required to continue the reaction by maintaining said zones inlcontact with a medium which is a liquid at said temperature and which has ahigh heat-conductlvity.

In testimony whereof I. aix my signature.

-HARRY D. GIBBS.' 

